Thermoplastic resins such as a polycarbonate resin (PC), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), a blend thereof and a mixture obtained by blending one or a plurality of the above resins with other resins bring about thermal decomposition (reduction in molecular weight) when they are heated and molten in various molding processes and lower in mechanical properties. The present invention relates to a resin additive which prevents thermal decomposition thereof and to a resin additive which prevents thermal decomposition and does not reduce the impact strength to a large extent.
Resin materials, particularly respective resins of PC, PBT and PET are heavily reduced in a molecular weight in melting by heating, so that the molecular weights have notably been reduced by heat given in various molding processes and shear stress exerted in kneading. Accordingly, it was difficult to recycle spools and runners produced in molding as well as recycling of the products.
According to researches made by the present inventors, the resins described above could be inhibited from lowering in a molecular weight in heating and melting by adding inorganic particles subjected to surface treatment with catechin to the resins, but there was the problem that the IZOT impact strengths were reduced.
Intensive researches of a resin additive of catechin continued by the present inventors have resulted in finding that thermo-plastic resins can be inhibited from lowering in a molecular weight in heating and melting by adding a resin additive obtained by subjecting inorganic particles to surface treatment with catechin to the above resins.
Further, the present inventors have found that thermo-plastic resins can be inhibited from lowering in a molecular weight in heating and melting and can be decreased in a reduction in an IZOT impact strength by adding to the above resins, a resin additive obtained by subjecting inorganic particles to surface treatment with catechin and further subjecting them to surface treatment with a coupling agent.
In addition thereto, the present inventors have found that thermoplastic resins can be inhibited from lowering in a molecular weight in heating and melting and can be prevented from lowering in an IZOT impact strength by adding to the above resins, a resin additive obtained by subjecting inorganic particles to surface treatment with catechin and further subjecting them to surface treatment with a phenone compound or saccharides, followed by further subjecting them to surface treatment with a coupling agent.
Accordingly, the first object of the present invention is to provide a resin additive which is obtained by subjecting inorganic particles to surface treatment with catechin and which can inhibit a resin from lowering in a molecular weight in heating and melting to prevent the resin from being deteriorated.
The second object of the present invention is to provide a resin additive which is obtained by allowing the surface of inorganic particles to be contacted with a catechin solution to treat them and further treating them with a coupling agent to thereby subject them to multilayer surface treatment and which not only can prevent a resin from lowering in a molecular weight in heating and melting but also can prevent the resin from lowering in an IZOT impact strength.
The third object of the present invention is to provide a resin additive which is obtained by allowing the surface of inorganic particles to be contacted with a catechin solution to treat them and further subjecting them to surface treatment with a phenone compound or saccharides, followed by further subjecting them to surface treatment with a coupling agent to thereby subject them to multilayer surface treatment and which attempts to thermally stabilize the resin by catechin and reduce the impact stress by the phenone compound or saccharides and strengthens the bond of the inorganic particles with the matrix resin to not only prevent the resin from being deteriorated in heating and melting but also prevent the resin from lowering in an IZOT impact strength.
The fourth object of the present invention is to provide a resin additive which not only provides a thermoplastic resin with heat stability in heating and melting the resin but also prevents the resin from lowering in an IZOT impact strength.
Further object of the present invention is to provide a resin additive which not only provides a thermoplastic polycarbonate resin, a thermoplastic polyester resin or a thermoplastic resin comprising these polycarbonate resin and polyester resin with heat stability in heating and melting the resin but also prevents the resin from lowering in an IZOT impact strength.
Another object of the present invention is to provide a resin additive which makes it possible to recycle the product.
Still another object of the present invention shall become more distinct from the following explanations.
It has been found that the preceding objects of the present invention can be achieved by:
1. a resin additive prepared by subjecting inorganic particles to surface treatment with catechin,
2. a resin additive prepared by subjecting inorganic particles to surface treatment with catechin and further subjecting them to surface treatment with a coupling agent,
3. a resin additive prepared by subjecting inorganic particles to surface treatment with catechin and then subjecting them to surface treatment with a phenone compound, followed by further subjecting them to surface treatment with a coupling agent, and
4. a resin additive prepared by subjecting inorganic particles to surface treatment with catechin and then subjecting them to surface treatment with saccharides, followed by further subjecting them to surface treatment with a coupling agent.
The resin additive of the present invention shall be explained below in further details.
The inorganic particles used in the present invention shall not specifically be restricted and may be any inorganic particles as long as they can effectively be used for the objects of the present invention. Specific examples thereof include silica salts such as silica, anhydrous silica, silica gel, talc, clay, mica aluminum silicate and kaolinite, alumina and salts thereof such as aluminates. In addition thereto, inorganic substances staying in a glass state, that is, glass can also be used as an inorganic material in the present invention. Various materials such as oxide glass, particularly silicate glass, powder of glass fiber, glass beads, glass balloon and fly ash can be used. Further, carbon and powder of carbon fiber can also be used as an inorganic particle. Among them, silica powder is produced in nature and therefore is excellent in profitability, so that it is preferably used. The particle size and form of the inorganic particles used shall not specifically be restricted and are suitably selected and used according to the kind and the use purposes thereof.
Next, catechin used in the present invention is a polyhydric phenol compound which is a polyoxy derivative of 3-oxyflavane and contained widely in plants in the natural world. It is said that catechin includes heterogeneous types having various molecular structures, and all ones are natural compounds, so that a lot of catechins having different structures are present. Catechin used in the present invention shall not specifically be restricted and may be any one as long as it is catechin which can effectively be used for the objects of the present invention. Catechin is called astringent juice. At present, catechin is used medically as a carcinostatic substance and industrially as a color fixing agent and a mordant for nylon. Catechin is very soluble in water and lower alcohols and therefore can be used in the form of a solution having a high concentration.
Four kinds of typical catechins are shown by the following formulas (a) to (d), respectively. Further, catechins are compounds contained widely in plants in the natural world as described above, and therefore it is readily presumed that they have partially different chemical structures. In the present invention, such polyhydric phenols shall not be distinguished from catechin and can be used synonymously therewith. 
The treatment of the inorganic particles with catechin is carried out by adding the inorganic particles to a solution of catechin and stirring to allow catechin to be adsorbed thereon, followed by filtering and drying the treated inorganic particles. In this case, with respect to the use amount of catechin, the inorganic particles are preferably treated in a solution containing catechin of 0.5 to 6.0% by weight (wt %) based on the inorganic particles to be treated. If the amount of catechin is smaller than 0.5 wt %, a heat stability effect for the resin is not revealed. On the other hand, even if the amount is more than 6.0 wt %, the effect remains unchanged, and therefore it is meaningless to use more amount than that. A solvent used in the treatment with catechin includes water, lower alcohols, tetrahydrofuran, toluene, benzene, acetone, acetonitrile, various ketones and esters. Water and lower alcohols are preferably used. The concentration of the catechin solution used in the present invention shall not specifically be restricted as long as it is not more than the saturated concentration of catechin at a temperature in allowing catechin to be adsorbed on the surface of the inorganic particles, and any concentration can be used. The temperature in allowing catechin to be adsorbed on the inorganic particles shall not specifically be restricted, but it is usually a room temperature. Two or more kinds of catechin can be used. The catechin-treated inorganic particles (abbreviated as particles 1) thus obtained can be used as a resin additive as they are. Further, this is treated with a coupling agent or treated with a phenone compound or saccharides and then further treated with a coupling agent, whereby the resin additive of the present invention can be prepared.
Next, the phenone compound used in the present invention is benzophenone or a derivative thereof and is suitably benzophenone itself. It is a matter of course, however, that the phenone compound may be a derivative of benzophenone such as benzophenone-2-carboxylic acid and benzophenone-4,4-dicarboxylic acid. The phenone compound functions in the same way as that of the coupling agent, and therefore the same amount as that of the coupling agent may be used. The use range thereof is preferably 0.4 to 4.2 wt % based on the catechin-treated inorganic particles. If the amount of the phenone compound is too small, the effect is not revealed. On the other hand, if the amount is too much, it reduces the mechanical strength of the resin by functioning as a plasticizer. Accordingly, both are not preferred.
The treatment of the particles 1 with the phenone compound is carried out by a method in which the phenone compound corresponding to 0.4 to 4.2 wt % of the particles 1 is dissolved in an organic solvent such as toluene and xylene and the particles 1 are added thereto and sufficiently stirred, followed by filtering and drying the treated particles 1 to obtain the phenone compound-treated particles 1 (hereinafter abbreviated as particles 2). In this case, the phenone compound and the particles 1 may be added to the organic solvent in any order. The treating conditions with the phenone compound shall not specifically be restricted, and the treating temperature, the treating time and the kind and the amount of the solvent used are suitably selected according to the kinds and the amounts of the inorganic particles and the phenone compound. Two or more kinds of the phenone compound can be used. The particles 2 thus obtained are further subjected to subsequent treatment with the coupling agent.
The saccharides used in the present invention include monosaccharides, oligosaccharides and polysaccharides, and various saccharides can be used. In particular, glucose, fructose, maltose and sugar are suited. It is a matter of course that polysaccharides such as anthocyanin, anthocyanidin, saponin and derivatives thereof can be used as well. The saccharides function in the same way as that of the coupling agent, and therefore the same amount as that of the coupling agent may be used. The use range thereof is preferably 0.4 to 4.2 wt % based on the inorganic particles treated with catechin. If the amount of the saccharides is too small, the effect is not revealed. On the other hand, if the amount is too much, it reduces the mechanical strength of the resin by functioning as a plasticizer.
The treatment of the particles 1 with the saccharides is carried out by a method in which the saccharides corresponding to 0.4 to 4.2 wt % of the particles 1 to be treated is dissolved in a solvent such as water and the above particles 1 to be treated are added thereto and sufficiently stirred to allow the saccharides to be adsorbed thereon, followed by filtering and drying the treated particles 1 to obtain the saccharides-treated particles 1 (hereinafter abbreviated as particles 3). In this case, the saccharides and the particles 1 may added to the solvent in any order. The treating conditions with the saccharides shall not specifically be restricted, and the treating temperature, the treating time and the kind and the amount of the solvent used are suitably selected according to the kinds and the amounts of the inorganic particles and the saccharides. Two or more kinds of the saccharides can be used. The method for treating with the saccharides shall not be restricted thereto, and any method can be used. The particles 3 thus obtained are further subjected to subsequent treatment with a coupling agent.
Silane base coupling agents are preferably used as the coupling agent used in the present invention. Among them, compounds having a terminal group such as an epoxy group, a vinyl group or an amino group are preferably used. To be specific, these silane base coupling agents include, for example, vinyl triethoxysilane, xcex3-methacryloxypropyl trimethoxysilane, xcex3-glycidoxypropyl trimethoxysilane, xcex3-aminopropyl triethoxysilane and trifluoropropylmethyl dimethoxysilane. The particularly preferred silane base coupling agents include xcex3-methacryloxypropyl trimethoxysilane, xcex3-glycidoxypropyl trimethoxysilane and trifluoropropylmethyl dimethoxysilane. The silane base coupling agent is used in a proportion of 0.4 to 4.2 wt %, preferably 0.8 to 2.5 wt % based on the weight of the inorganic particles treated with catechin. If the surface-treated amount with the coupling agent is small, the effect is not revealed. On the other hand, if the amount is too much, the coupling agent functions as a plasticizer in the resin and reduces the mechanical properties of the resin. Accordingly, both are not preferred.
The treatment of the particles 1, 2 or 3 with the coupling agent can be carried out by various methods, and it can be carried out, for example, by a method in which the coupling agent corresponding to 0.4 to. 4.2 wt % of the particles 1 or the particles 1 used for producing the particles 2 or 3 is dissolved in water or an organic solvent such as toluene and xylene and the particles 1, 2 or 3 to be treated with the coupling agent are added thereto and sufficiently stirred to allow the coupling agent to be adsorbed thereon, followed by filtering and drying the treated particles 1, 2 or 3 to obtain the coupling agent-treated particles 1, 2 or 3 (the resin additive of the present invention). In this case, the coupling agent and the particles 1, 2 or 3 may added to the solvent in any order. The treating conditions with the coupling agent shall not specifically be restricted, and the treating temperature, the treating time and the kind and the amount of the solvent used are suitably selected according to the kinds and the amounts of the inorganic particles and the coupling agent. Two or more kinds of the coupling agents can be used in combination. In addition thereto, a method for treating with the coupling agent includes a method in which the coupling agent or a solution of the coupling agent is sprayed directly on the particles 1, 2 or 3. In this case, it is more effective to leave the particles 1, 2 or 3 subjected to spraying treatment for standing in a closed vessel at a room temperature to about 40xc2x0 C. for several days to about one month after spraying. Further, there can be used, a method in which the particles 1, 2 or 3, the coupling agent and a resin are molten and kneaded at the same time, but the present invention shall not be restricted to these methods, and any methods may be used. With respect to the treating order of the inorganic particles in producing the resin additive of the present invention, treatment with catechine is usually carried out at first, or treatment with the phenone compound or the saccharides is carried out, and treatment with the coupling agent is carried out at last. However, this treating order shall not be restricted thereto, and the treatment may be carried out in any order.
The resin to which the resin additive of the present invention is added shall not specifically be restricted, but polycarbonate resins and thermoplastic polyester resins, particularly polyethylene terephthalate and polybutylene terephthalate are suited. Further, blends thereof and blended resins of one or a combination of a plurality thereof and other resins, for example, PC/ABS, PBT/ABS, PC/PBT, PC/PET and PC/polystyrene are preferably used.
In general, the resin additive of the present invention is added to a resin in a proportion of 0.5 to 3.5 wt % based on the resin.
The inorganic particles subjected to surface treatment with catechin allow the molecules of catechin to stick strongly on the surfaces thereof. On the other hand, when the resin is thermally decomposed, radical molecules are produced, and if the radical molecules can be turned to stable molecules, the resin can be inhibited from being decomposed. Catechin has many hydroxyl groups, and these hydroxyl groups trap radicals produced by decomposition of the resin. However, it is considered that a lot of the hydroxyl groups are present as well on the outside of catechin which sticks firmly on the surface of the inorganic particles, and as a result thereof, it is considered that the inorganic particles subjected only to surface treatment with catechin can inhibit the resin from being decomposed but do not have so much wettability to the matrix resin. This results in preventing the resin from combining firmly with the inorganic particles. Accordingly, the IZOT impact strength results in lowering from the intrinsic value of the resin to a large extent. It is expected that two matters of a stabilization of the resin and an inhibition of a reduction in the IZOT impact strength can be achieved at the same time by allowing the inorganic particles subjected only to surface treatment with catechin or the inorganic particles obtained by further subjecting them to surface treatment with the saccharides or the phenone compound to adhere firmly to the matrix resin with the coupling agent. On the other hand, it is considered that the phenone compound or the saccharides which is present between the catechin layer and the coupling agent layer functions as a so-called cushion which disperses a stress exerted on the resin, whereby an effect to prevent a larger reduction in the IZOT impact strength can be obtained. However, the present invention shall not be restricted by such reason.
The inorganic particles thus obtained subjected only to surface treatment with catechin or the inorganic particles obtained by further subjecting the inorganic particles subjected to surface treatment with catechin or the inorganic particles subjected to surface treatment with catechin and subsequently to surface treatment with the phenone compound or the saccharides to surface treatment with the coupling agent become, as described above, a resin additive which can inhibit a reduction in the molecular weight of the resin or can inhibit not only a reduction in the molecular weight but also a reduction in the IZOT impact strength.
As shown in the following examples and comparative examples, the resin additive of the present invention obtained by subjecting the inorganic particles only to surface treatment with catechin can inhibit a reduction in the molecular weight of the thermoplastic resin in heating and melting. Further, the resin additive obtained by further subjecting the inorganic particles subjected to surface treatment with catechin to surface treatment with the coupling agent, or the resin additive obtained by subjecting the inorganic particles to surface treatment with catechin, then to surface treatment with the phenone compound or the saccharides and subsequently to surface treatment with the coupling agent can inhibit as well the IZOT impact strength. Accordingly, the resin additive of the present invention has the effect that it can inhibit a reduction in the molecular weight of the thermoplastic resin such as PC, PBT, PET and blended resins thereof or not only can inhibit a reduction in the molecular weight in heating and melting but also can decrease a reduction in the IZOT impact strength.